Panel suitable for assembling a waterproof floor or wall covering, method of producing a panel

ABSTRACT

Panel suitable for assembling a waterproof floor or wall covering from a plurality of said panels, wherein the panel has a substantially planar top surface, and a substantially planar bottom surface,
         the panel having a laminated structure of layers which comprises:
           a flexible core layer which basically is composed of a material which is relatively low in density and is provided with voids in the form of air pockets, and   a rigid top layer which comprises a support layer that is basically composed of a material that is relatively high in density and which is virtually devoid of air pockets,   
           wherein the thickness of the core layer is smaller than the thickness of the support layer, preferably in a ratio of 0.5 or less, more preferably in a ratio between 0.5 and 0.10.

The invention relates in a first aspect, to a panel suitable for assembling a waterproof floor or wall covering from a plurality of said panels, wherein the panel has a substantially planar top surface, and a substantially planar bottom surface,

-   -   the panel having a laminated structure of layers which         comprises:         -   a flexible core layer which basically is composed of a             material which is provided with voids in the form of air             pockets and hence is relatively low in density, and         -   a rigid top layer which comprises a support layer that is             basically composed of a material that is virtually devoid of             air pockets and hence is relatively high in density,     -   and wherein the core layer has a lower density than the top         layer.

The invention relates in a second aspect to a method of producing a panel according to the first aspect of the invention.

In the field of floor and wall coverings, initially panels were developed based on wood materials or derivatives thereof. A major disadvantage however, is the hygroscopic nature of such materials, which reduces its suitability as a waterproof covering, and affects the lifetime and durability of such panels.

As an important alternative, in U.S. Pat. No. 9,212,494 a panel has been proposed based on layers from polyvinyl compounds. The use of such compounds is advantageous as they are water resistant, and are relatively light in weight. The panel as proposed has a laminated structure of layers according to a sandwich type: it comprises a top layer, a substrate layer (actually the central, main layer) and a backing layer. The substrate layer has a relatively low density, and is made from a foamed synthetic material. The top layer and backing layer are of a polyvinyl compound, wherein at least the top layer has a higher density than the substrate layer. Accordingly, the substrate layer has more flexible properties than the top layer which is of a more rigid character.

In this panel the thickness of the substrate layer is of such size, that it allows for the provision of interconnecting profiles of a tongue and groove type which thus form an integral part of the substrate layer.

In regard of the applied density of the substrate layer, US494 teaches to strike a fine balance: on the one hand, the density should be high enough to avoid migration effects relating to any unevenness of the underlying surface being transmitted towards the upper surface of the panel. Furthermore, a too soft character of the layer is to be avoided in order to prevent deformation by forces applied on the upper surface of the panel during its use. Also the propagation of sound becomes an issue in using too soft materials for the panel. On the other hand, the density should not become too high, in order to avoid a too stiff panel that creates sound boxes between the panel and the underlying surface at spots where any unevenness is present. Accordingly, US494 teaches the substrate layer should have a balanced density which lies between 450 and 900 kg/m3.

In terms of its practical properties for the end-user, the panel proposed in US494 does achieve an adequate noise level reduction and sufficient waterproof quality, however other properties of the panel such as rigidity and indentation performance are compromised, to an actually inadequate or unsatisfactorily degree.

In conclusion, when overviewing the panels known from the prior art, still a general need exists in the field to develop a further improved panel which not only has interesting waterproof and acoustic properties, but which in addition has an adequate rigidity and/or resistance to indentation.

In the above context, it is an objective of the invention to meet the above general need, by developing a technical solution which takes away completely or in part, one or more of the disadvantages relating to panels known from the prior art.

The above objective of the invention, is met by the provision of a panel according to the above preamble, wherein the thickness of the core layer is smaller than the thickness of the support layer, preferably in a ratio of 0.5 or less, more preferably in a ratio between 0.5 and 0.10. Most preferably, the ratio is between 0.5 and 0.25.

It has been found by the inventors, that by reducing the thickness of the core layer in comparison to the support layer, it is possible to achieve a panel with adequate waterproof and acoustic properties, which has at the same time a sufficient rigidity and/or an adequate resistance to indentation.

There is moreover an additional technical advantage gained, in that the panel as a whole is less susceptible to deformation, i.e. curling as a result of temperature and humidity cycles it may be subjected to during use is significantly reduced using relatively thin core layers in the panel.

Preferably, in the panel according to the invention, the support layer is directly or indirectly provided onto the top side of the core layer.

For instance, the support layer may be laminated to the core layer by applying sufficient heat and pressure, or alternatively may be glued to one another by applying an adhesive layer in between both layers.

With specific preference, in the panel according to the invention, the core layer has a thickness in the range of 0.5 to 3.0 mm, preferably 0.8 to 1.5 mm.

With further specific preference, in the panel according to the invention, the support layer has a thickness in the range of 2.0 to 8.0 mm, preferably 2.5 to 4.0 mm.

It is noted that in the context of the invention, the maximum overall thickness of the panel lies in the range of 4 to 15 mm, more preferably between 4.5 and 8.0 mm.

In a preferred embodiment of the panel according to the invention, the core layer has a density of 100 up to 300 kg/m3. This density has been found to strike an adequate balance in regard of achieving all the desired properties according to the objective of the invention.

In the panel according to the invention, the intrinsic voids in the material of the core layer may have the form of a closed cell and/or open cell structure.

In particular, it is preferred in the panel according to the invention that the material of the core layer has a foam structure. The foam structure consists basically of a matrix in which closed and/or open cells are present. The foam structure is typically obtained by adding blowing agents to a melt, before it is formed and hardened into its final shape. As the foam structure has a lower density than a solid structure, the weight of the core layer is further reduced which is advantageous for the panel. The foam structure has furthermore the advantage of improved sound dampening properties in comparison to a solid structure.

In a further preferred embodiment of the panel according to the invention, the support layer has a density of at least 1200, more preferably at least 1400, and most preferably at least 1600 kg/m3. Dependent on the specific built-up of the panel, an appropriate density generally lies in the range of 1800 to 2100 kg/m3.

As such, the support layer contributes to a substantial degree to an adequate rigidity and resistance to indentation.

Furthermore, in the panel according to the invention, the support layer has a rigidity of at least 2000 N/mm2 when measured according to the standard EN310.

It is preferred for the panel according to the invention that is has an overall rigidity of at least 2000 N/mm2 when measured according to the standard EN310. Preferably the overall rigidity shall be in the range of 3000-6000 N/mm2, more preferably in the range of 4000-5000 N/mm2 (measured according to the standard EN310).

In the panel according to the invention, it is preferred that the material of the core layer comprises a foam material from PE, EVA, PS, PP, PU, or melamine, or alternatively cork.

In the panel according to the invention, it is preferred that the material of the support layer comprises a thermoplastic material, preferably PVC, more preferably PVC that is virtually free from plasticizer and contains CaCO3 as filler material, wherein most preferably CaCO3 is present in a wt. % content of 60.

In a further preferred embodiment of the panel according to the invention, the material of the support layer contains a reinforcing material, such as a fiberglass net or mesh.

As such, the support layer is further strengthened in view of its intended use in the panel according to the invention.

Furthermore in the panel according to the invention, it is preferred that the top layer comprises a wear layer, and a décor layer on top of the support layer, the wear layer being optionally provided with a coating.

These additional layers make the panel more suitable for its intended use as a waterproof floor or wall covering.

The coating may be a from a material made from urethane, acrylic or oil compounds, and it is preferably 0.05 to 0.10 mm thick. The wear layer may made from a thermoplastic compound, including PVC; or alternatively from wood, paper or paper impregnated with melamine. The wear layer is preferably 0.15 to 0.50 mm thick. The décor layer is about 0.05 to 3.0 mm thick, and is made from any suitable material amongst others: PVC, wood, paper, paper impregnated with melamine, and cork. Further, the décor layer is provided with a decorative side that may be formed by digital printing.

As commonly applied in top layers of panels, the edges at the top surface may be provided with a bevel that extends over the wear layer.

According to a preferred embodiment, in the panel the bottom side of the core layer is directly or indirectly provided with a backing layer.

The backing layer contributes to evening out any unevenness on the underlying surface on which the panel is laid, and may contribute to the rigidity of the panel. In addition, the backing layer may have additional features such as a grip effect and antibacterial properties.

The backing layer has a preferred thickness of 0.5 to 5.0 mm; more preferably 0.8 to 2.0 mm. The material of the backing layer is a thermoplastic material, wood, paper or paper impregnated with melamine.

Preferably the material of the backing layer is PVC, more preferably a PVC that is virtually free from plasticizer and contains CaCO3 as filler material, most preferably in a wt. % content of 60.

Alternatively, the material of the backing layer may be a flexible vinyl compound with a plasticizer content of at least 5 wt. %.

With particular preference, the panel according to the invention has at least four substantially linear side edges, preferably having a rectangular design.

This design makes the panel most suitable for assembling a floor or wall covering from a plurality of panels.

In the panel according to the invention, is has a special preference that the linear side edges comprise at least one pair of opposite side edges which are provided with interconnecting coupling means for interconnecting one panel within another.

As such a ‘floating’ covering can be assembled by interconnecting the individual panels with each other at their connecting sides without the need to use additional coupling means such as adhesives.

Preferably the panel according to the invention, comprises two pairs of opposite side edges which are provided with interconnecting coupling means.

When the panel according to the invention is provided with interconnecting coupling means, these preferably comprise a tongue and a groove wherein the tongue is provided on one side edge of one pair of opposite side edges, and the groove is provided on the other side edge of the same pair of opposite side edges. Such a design of coupling means is well-known in the art and has proven highly suitable for panels for floating floors.

Additionally, in the panel according to the invention, it is preferred that the interconnecting coupling means have an interlocking feature which avoids free movement of interconnected panels.

Such an interlocking feature may be a projection and a respective recess provided on the respective opposite side edges by which neighbouring panels interlock with each other.

When the panel according to the invention is provided with interconnecting coupling means, it is preferred that these means are provided as an integral part of the support layer.

As such, the coupling means are made from relatively stiff material which contributes to a secure connection, a robust embodiment of the coupling means, and a relative ease for the end-user in regard of coupling the means together.

Preferably in the panel according to the invention, the core layer and/or the support layer is an extruded sheet material. Such a layer is easily produced, and the extrusion process is suitable for the formation of a sheet having a foam structure—which is a preferred structure for the core layer.

The individual layers constituting the rigid top layer are formed by lamination under high pressure, co-extrusion or calendering.

A special aspect of the invention relates to a waterproof floor or wall covering composed of a plurality of assembled panels, wherein the panels are conform the first aspect of the invention. Such a covering profits from the same advantages as set out already above.

In the case that the panels are provided with interconnecting coupling means, the panels are assembled by interconnecting the interconnecting coupling means from respective neighbouring panels.

In a second aspect, the invention relates to a method of producing a panel according to the first aspect of the invention comprising the steps of:

-   -   a) providing a flexible core layer which basically is composed         of a material which is relatively low in density and is provided         with voids in the form of air pockets;     -   b) providing a rigid top layer which comprises a support layer         that is basically composed of a material that is relatively high         in density which is virtually devoid of air pockets;     -   c) adhering the rigid top layer to the top side of the core         layer, preferably by applying an adhesive at the interface of         the core and top layer.         characterized in that     -   the thickness of the core layer is smaller than the thickness of         the support layer, preferably in a ratio of 0.5 or less, more         preferably in a ratio between 0.5 and 0.10.

The method according to the invention provides a new and expedient way to provide a panel according to the first aspect of the invention.

In consistency therewith, the method according to the second aspect of the invention may include any of the preferred features of the panel according to the first aspect of the invention.

The following dimensions and properties are preferred for the panel according to the invention:

-   -   overall thickness of the panel: 4.5 to 8.0 mm     -   thickness of the rigid top layer approx. 3.0 mm     -   thickness of the core layer approx. 1.0 mm     -   thickness of the backing layer approx. 1.0 mm     -   overall width of the panel: 120-600 mm     -   overall length of the panel: 300-2500 mm

In respect of the core layer being based on a foam material the following properties are preferred:

-   -   pore size: 0.01 to 0.5 mm     -   pore volume: 20 to 50%     -   density: 100-300 kg/m3

FIGURES

The invention will be further explained with reference to the appended figures wherein:

FIG. 1 shows in perspective a preferred embodiment of the panel according to the invention;

FIG. 2 shows a cross-section of the preferred embodiment of the panel according to the invention;

FIG. 3 shows a cross-section of several variants of the panel according to the invention;

FIG. 4 shows a cross-section of a panel as proposed in relevant prior art.

FIG. 1 shows a panel 1 suitable for assembling a waterproof floor or wall covering by interconnecting a plurality of said panels with each other, wherein the panel has a substantially planar top surface 3, and a substantially planar bottom surface 5, at least four substantially linear side edges 6 a,6 b,6 c,6 d comprising at least one pair of opposite side edges 6 a,6 c which are provided with interconnecting coupling means 7,8 for interconnecting one panel within another, the panel having a sandwich structure which comprises a core layer 10 basically composed of a foam material, a rigid top layer 12 and a backing layer 14.

FIG. 2 shows the same embodiment as FIG. 1 in cross-section, wherein the interconnecting coupling means 7,8 comprise a tongue 7 and a groove 8, each having an interlocking feature 20 a (a projection) and 20 b (a recess) which avoids free movement of interconnected panels when the tongue of one panel is inserted in the groove of another neighbouring panel.

The core layer 10 is composed of a foam structure based on EVA, which has soft and flexible properties. The foam structure of the core layer 10 contains voids in the form of air pockets which are schematically depicted by small circles 10 a.

The rigid top layer 12 comprises a support layer 12 a, a décor layer 12 b, a wear layer 12 c, and a coating 12 d. The support layer 12 a is a rigid, high density PVC material that is free from plasticizer.

The backing layer 14 is composed of an extruded PVC material that is free from plasticizer, and consequently is rigid.

The shown thicknesses are roughly indicative for the actual thicknesses that are used in the panel of the invention. The overall thickness of the shown panel is approximately 6 mm.

FIG. 3 shows several variants of the panel in regard of the design of the side edges 6 a and 6 c. The laminated structure of the layers in FIG. 3 is the same as that of layers 10, 12 and 14 as depicted in FIG. 2.

FIG. 3a shows a design of side edges 6 a and 6 c as depicted in FIG. 2 which allows for an interlocking of two complementary side edges by an angling-in movement;

FIG. 3b shows a design of side edges 6 a and 6 c being simply a flat surface, wherein the side edges may be interlocked by applying an adhesive material on the contacting side edges of neighbouring panels;

FIG. 3c shows a design of side edges 6 a and 6 c being provided with a classic groove 8 and tongue 7 design, which requires a horizontal shifting movement to interconnect two panels.

FIG. 3d shows a design of side edges 6 a and 6 c being provided with another classic groove 8 and tongue 7 design, that allows for interconnection by a vertical or drop-down movement.

Importantly, in all the above tongue and groove designs shown, both types of interconnecting coupling means form an integral part of the support layer 12 a.

FIG. 4 shows a cross-section of a panel as proposed in relevant prior art, for comparative reasons and in connection to the comparative example given below.

Comparative Example

The advantageous technical effect of the invention will be further substantiated with reference to the following comparative example:

Example I WPC Flooring Product (Prior Art)

A so-called WPC flooring panel was produced in line with the disclosure of U.S. Pat. No. 9,212,494, and attached FIG. 4.

Essentially, the core layer of foam material forms the main layer of the panel for constituting more than half the total thickness of the panel (in line with FIG. 4). Furthermore, the tongue and groove profiles are an integral part of the core layer. The density of the core layer is approx. 750 kg/m3.

The top layer provided on the core layer of foam material, is more dense and has a density of 1600 to 1800 kg/m3 which is above the value of the core layer.

The backing layers consisted of an EVA and PE cushion layer with a density of approx. 200 kg/m3.

Example II Panel According to the Invention

A specimen panel according to the invention and as depicted in FIG. 2, was produced having the following properties:

Support Layer:

-   -   Made from PVC that is virtually free from plasticizer and         contains CaCO3 as filler material, wherein CaCO3 is present in a         wt. % content of 60.     -   thickness of 2.5 to 3.0 mm.     -   density of 1800 to 2000 kg/m3     -   rigid, solid properties

Core Layer:

-   -   Made from EVA, PE or PS foam     -   Thickness of 0.8 to 1.5 mm     -   Density of 100 to 300 kg/m3     -   Soft, flexible properties

Backing Layer:

-   -   Made from PVC that is virtually free from plasticizer and         contains CaCO3 as filler material, wherein CaCO3 is present in a         wt. % content of 60.     -   thickness of 0.8 to 2.0 mm.     -   density of at least 1600 kg/m3     -   rigid, solid properties

Common Features

Both panel I and II, were provided with similar finishing layers on its top surface, i.e. a coating, a wear layer, and a décor layer. The materials used were also similar and are commonly used in the art.

Comparative Tests

Both panels were subjected to the following tests:

-   -   acoustic tests; in accordance with the following standards:     -   ISO 10140-1, ISO 717-2, ASTME2179-03, ASTME989-06.     -   indentation tests; in accordance with the following standards:     -   ASTM 1914.     -   Rigidity tests; in accordance with the following standards:     -   EN 310.

The below table shows the results that were obtained by the above tests.

Indentation Acoustic performance performance Rigidity Test name Improvement Reducing of Residual Modulus of of impact sound impact sound indentation elasticity Test norms ISO 10140-1, ASTME2179-03, ASTM 1914 EN 310 ISO 717-2 ASTME989-06 Test results ΔLw ΔIIC MOE value Example II 21 dB-22 dB 25 dB-26 dB 1%-5% 3000-6000 N/mm2 (Invention) Example I   21-22 dB 25 dB-27 dB  8%-25%  800-2000 N/mm2 (prior art)

From the above table, one derives directly that the panel according to the invention achieves not only adequate acoustic properties, but in addition also has satisfactorily values in terms of both indentation resistance and rigidity.

For combining all these three properties to an adequate extent, the invention is arguably an improvement over the prior art, which in contrast shows inadequate values both in terms of indentation resistance and rigidity. 

1. A panel suitable for assembling a waterproof floor or wall covering from a plurality of panels, wherein the panel has a substantially planar top surface, and a substantially planar bottom surface, the panel having a laminated structure of layers which comprises: a flexible core layer which is substantially composed of a material which is provided with voids in the form of air pockets and hence is relatively low in density, and a rigid top layer which comprises a support layer that is substantially composed of a material that is virtually devoid of air pockets and hence is relatively high in density, and wherein the core layer has a lower density than the top layer, wherein a thickness of the core layer is smaller than a thickness of the support layer, in a ratio of 0.5 or less.
 2. The panel according to claim 1, wherein the support layer is directly or indirectly provided onto a top side of the core layer.
 3. The panel according to claim 1, wherein the core layer has a thickness in the range of 0.5 to 3.0 mm.
 4. The panel according to claim 1, wherein the support layer has a thickness in the range of 2.0 to 8.0 mm.
 5. The panel according to claim 1, wherein the core layer has a density of 100 up to 300 kg/m3.
 6. The panel according to claim 1, wherein the support layer has a density of at least 1200 kg/m3.
 7. The panel according to claim 1, wherein the panel has an overall rigidity of at least 2000 N/mm2 when measured according to the standard EN310.
 8. The panel according to claim 1, wherein the material of the core layer comprises a foam material from PE, EVA, PS, PP, PU, or melamine, or alternatively cork.
 9. The panel according to claim 1, wherein the material of the support layer comprises a thermoplastic material.
 10. The panel according to claim 1, wherein the top layer comprises a wear layer and a décor layer on top of the support layer.
 11. The panel according to claim 1, wherein a bottom side of the core layer is directly or indirectly provided with a backing layer.
 12. The panel according to claim 1, wherein the panel has at least four substantially linear side edges having a rectangular design.
 13. The panel according to claim 12, wherein the linear side edges comprise at least one pair of opposite side edges which are provided with interconnecting coupling means for interconnecting one panel within another.
 14. The panel according to claim 13, wherein the interconnecting coupling means comprise a tongue and a groove wherein the tongue is provided on one side edge of one pair of opposite side edges, and the groove is provided on the other side edge of the same pair of opposite side edges.
 15. The panel according to claim 13, wherein the interconnecting coupling means are provided as an integral part of the support layer.
 16. The panel according to claim 1, wherein the core layer and/or the support layer is an extruded sheet material.
 17. A waterproof floor or wall covering composed of a plurality of assembled panels, wherein the panels have a substantially planar top surface, and a substantially planar bottom surface, the panels having a laminated structure of layers which comprises a flexible core layer which is substantially composed of a material which is provided with voids in the form of air pockets and hence is relatively low in density, and a rigid top layer which comprises a support layer that is substantially composed of a material that is virtually devoid of air pockets and hence is relatively high in density, and wherein the core layer has a lower density than the top layer, wherein a thickness of the core layer is smaller than a thickness of the support layer in a ratio of 0.5 or less.
 18. A method of producing a panel suitable for assembling a waterproof floor or wall covering from a plurality of panels, wherein the panel has a substantially planar top surface, and a substantially planar bottom surface, the method comprising the steps of: a) providing a flexible core layer which is substantially composed of a material which is relatively low in density and is provided with voids in the form of air pockets; b) providing a rigid top layer which comprises a support layer that is substantially composed of a material that is relatively high in density which is virtually devoid of air pockets; c) adhering the rigid top layer to the top side of the core layer by applying an adhesive at the interface of the core and top layer; wherein the thickness of the core layer is smaller than the thickness of the support layer, preferably in a ratio of 0.5 or less.
 19. The panel according to claim 9, wherein the material of the support layer is PVC that is virtually free from plasticizer and contains CaCO3 as filler material, wherein the CaCO3 is present in a wt. % content of
 60. 20. The panel according to claim 10, wherein the wear layer is provided with a coating. 